Radiation therapy is a treatment for cancer which transmits radiation in the form of light waves or high-speed particles, using high-energy radiation to destroy cancer cells and inhibit their growth to achieve the purpose of treating cancer, and is commonly administered to patients who cannot tolerate surgery or for the treatment of recurrence after surgery.
Radiation therapy techniques are divided into two categories, one is teletherapy, and the other is brachytherapy. Teletherapy is an external radiotherapy which places the radioactive source outside the body. The generated beam of radiation passes through the body and make the treated area receive radiation exposure. Brachytherapy generates beam of radiation by the radioactive source in a catheter which is inserted into a body cavity and placed in the tumor tissue or near the surroundings of the tumor tissue to make the tumor receive radiation exposure to radiation to achieve the purpose of treatment.
Brachytherapy is suitable for treating tumors growing in a body cavity, and is widely used to treat cervical cancer, along with endometrial cancer, nasopharyngeal cancer, prostate cancer and other tumors that grow wherever a catheter can be placed.
Since the radioactivity is inversely proportional to the square of the distance from the source, when administrating brachytherapy, normal tissues or organs which are farther from the source are exposed to far less radiation than those in central areas. Such contrast can reduce radiation damage to normal tissues, and therefore the side effects caused by radiation therapy or the incidence of sequelae after radiation therapy can also be reduced.
Currently, brachytherapy instruments used in domestic market are mainly for high-dose rate brachytherapy, which shall be at the dose rate of more than 12-Gy/hour, while in Europe and in the United State, low-dose rate brachytherapy is more commonly used, and the dose rate shall be under 2-Gy/hour. Low-dose rate brachytherapy performs better biological properties than high-dose rate brachytherapy, since in a low-dose rate brachytherapy, the radiation damage the normal cells receive has a better chance to be repaired, and hence theoretically the incidence of sequelae is lower than the latter.
However, when comparing to the low-dose brachytherapy, the high-dose rate brachytherapy has many advantages: (1) less expensive, patients can be treated as outpatients without hospitalization for days; (2) the treatment time is short and therefore it is more comfortable for patients; (3) the treatment time is short, so the positional stability of the source which is temporarily placed in the body is higher; (4) radiation therapy practitioners do not have the concern of unnecessary radiation dose exposure.
Nevertheless, when brachytherapy is administered, it also causes damages to the exposed normal tissues surrounding the tumor, and the occurrence of the side effects of radiation therapy is exactly related to the exposed area and dose. Hence, the closer to the source the normal tissues are, the higher dose they receive, and the greater the side effect is.
Generally side effects of radiation therapy are fatigue, skin redness and fragile skin of radiation area. Body parts which are rubbed frequently such as armpit and groin etc., are prone to inflammation and scratch. Abdominal radiotherapy often causes diarrhea as a side effect.
Radiation therapy to the head and neck may cause thick saliva, low saliva production, altered taste, redness of the oral mucosa, dry mouth, dysphagia and painful swallowing, even loss of appetite and so on.
On the other hand, since the radiation therapy is administered by inserting a catheter into the body cavity to treat the surrounding tumor tissues. A conventional catheter, such as an Elekta's Bonvoisin-Gerard Esophageal Applicator product, is placed in a body cavity and the whole section of the catheter is inflated to keep the cavity open. This helps the delivery of a radioactive source. However, the way that inflating the whole section of the catheter to keep the cavity open causes discomfort to patients during treatment.
Therefore, designing an apparatus which abates the patients' discomfort caused by the administration of radiation therapy, and decreasing the scope of normal tissue exposure to reduce side effects from the treatment, is really an issue remains to be solved currently.